Control system for multiple-point measuring instrument



www giga-37e "oct 27, 1953 CONTROL. s ssr'x-:M FOR MULTIPLE-Pomf-Mmsuhmc INS'WMENT n. j

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` Filed Dec. 23,` 1.949

INVEN TOR. wm. MAoAM ATTORNEYS INVENTOR. WILL MADAM SS BY WWMM ATTORNEYS Patented Oct. 27, 1953 CONTROL SYSTEM FOR MULTIPLE-POINT MEASURING INSTRUMENT Will McAdam, Ambler, Pa., assigner to Leeds and l 'i Northrup Company, Philadelphia, Pa., a corf poration of Pennsylvania r Application December 23, 1949, Serial No. 134,670

8 Claims. (Cl. 340-213) .This invention relates to the indicating, recording and/or control in sequence from a distance of a plurality of variable conditions and 'has for an object the provision of a system for maintaining in synchronism the operation of a remotely located circuit controller with the meas- 'uring and/or controlling equipment.

In the control of many processes, and in studies made of various kinds of equipment, it 1s frequently desirable and necessary to measure in sequence and as rapidly as possible the magnitudes of a plurality of conditions, such astemvided as to the magnitudes or change in magnitudes of a plurality of conditions in a process or equipment.

Where the measuring instrument is located suiciently near the apparatus under test, a transfer switch has in the past been provided to connect in sequence the condition-responsive devices into the measuring network, the transfer switch being driven by the measuring instrument. However, where it is not feasible to utilize the measuring instrument near the site of the measurements, the problem of maintaining synchronism between a remotely located transfer switch and the measuring instrument has been difficult of solution and has been solved only by relatively complicated control systems.

' Additionally, it has been deemed desirable to f include a signalling system to indicate the particular condition under measurement and, likewise, to provide a record of the change in each condition which, by its distinctive character on a record chart, may be distinguished from other records appearing thereon.

In the past the transfer switch of the measuring instrument has been located within the instrument housing and, hence, the temperature of the switch-follows that within the housing i which may not be of uniform value, giving rise i to the possibility of differing temperatures in diiferent parts of the measuring circuit which, of course, gives rise to thermal'effects on lowlevel measuring circuits. Accordingly, it is deemed desirable in such cases to locate the transfer switch externally of the measuring instrument and to provide a transfer switch Which is specially designed to minimize disturbances in the measuring circuit. such a transfer switch not being particularly adapted for direct drive from the measuring instrument. The present invention is particularly applicable to such applications, though the measuring apparatus as a 'whole is not remotely located from the conditionresponsive devices, such as the thermocouples.

Itis a further object of the present invention to provide a control system which is reliable, simple, and which maintains synchronism between the measuring instrument and a remotely located transfer switch. M

A further object is to provide automatic means to re-"establish synchronism between the measperature, in order that information may be prouring instrument and the transfer switch Whenever the one gets out of step with the other, and also to provide a signalling system which not only indicates the particular condition under measurement, but which also signals the ioperator that the 'transfer switch and the measuring instrument are out of synchronism.

In carrying out the invention in one form thereof a transfer switch driven by any suitable driving means remotely located from the measuring instrument is provided with control circuits which not only control the driving means sequentially to connect the condition-responsive devices to the measuring instrument, but which also maintains the operation of the transfer switch in synchronism or in predetermined angular relation with a rotatable element of the measuring instrument.

Included in the control circuits are signalling l circuits' for producing an indication by signal lamps not only to assure the operator of proper synchronous operation, but also distinctively to inform him whenever there is asynchronous operation. More speciiieally, there is provided a circuit controller driven by the measuring instrument in sequence through a plurality of positions. A circuit is established through the instrument-driven circuit controller to the remotely located driving means or motor which not only causes it to move from one circuit-controlling position to another, but also to maintain its transfer switch in synchronous or predetermined timed relation with the instrument-operated cirl cuit controller and to move it into synchronous relation whenever the one gets out of step with the other. The motor is provided with automatic braking means and in the event of asynchronous operation, greatly reduced voltage is applied to the signalling lamps to reduce their illumination to indicate to the operator that the transfer switch is then out of step with the measuring instrument.

For a more detailed description of the invention and for further objects and advantages thereof, reference is to be had to the following description taken in'conjunction with the accompanying drawings, in which:

Fig. 1 diagrammatically illustrates a Wiring diagram with the several circuit-controllers and .transfer switches diagrammatically shown; and

Fig. 2 diagrammatically illustrates a modification of the invention.

Referring to the drawings, the invention in one form has. been shown .as applied to a multiplepoint measuring instrument I which may be of any suitable type, such for example as that disclosed in Ross et al. Patent 2,113,069 and which .includes therein the disclosure of a transfer 'Athermocouple remains connected in the circuit until the measuring instrument has operated to 'measure the temperature to which it is subjected and has printed on the record sheet a number windicative of the particular thermocouple then 'connected to the circuit and at a position on the "chart which is indicative of the magnitude of the temperature. I A

It is to be understood that the present invention has been applied to an instrument of the 'character disclosed in said Ross et al. patent, and v`in Fig. 1 of the accompanying drawing the print- 'wheel II of instrument I0 is similarly operated conductor 38, signal lamp 35a, and by conductor 33 to the other supply line 24. Thus, alternating current flows through the capacitor 31, the current being adequate to energize the signal lamp 35a to normal brilliance. The capacitor 31 serves `:to block from the lamp unidirectional current flowing in the circuit including the rectifier 29, while resistor 36 aids the capacitor in limiting the 'magnitude of the current 110W. By'decreasing the size of thel capacitor, the resistor 36 may be omitted. l

The bank 35 of signal lampslmay be located as desired',l either adjacent the measuring instru- 'ment I0 or near the remote location of the thermocouples Iii-2|. Obviously, banks of sig- .'nal lights may' be located at both positions, the two banks being connected in parallel under the and the connection indicated by the broken line 7 4I2 corresponds with the shaft 30 of Fig. 13 of said Ross et al. patent for rotating in synchronism "with the printwheel I I multiple-point switches I3 and I4 and the cam I'o'a which operates a circuit interrupter. e

As shown, a thermocouple I 6 is connected to 'the input circuit of instrument I0 through preamplier 22. that therinocouples I12I are to be connected `in sequence to the instrument I0.

It will, of course, be understood Though not always needed, where the thermocouples Iii-2| have low signal outputs and are remotely located from the measuring instrument I0, it is desirable to include in the input circuit thereto the preamplifier 22 to increase the amplitude of the output from each thermocouple to a value at least within the range for proper operation of the inlstrument IU.

With the parts in their illustrated positions there is established between alternating current -supply lines 23 and 24 a circuit for flow o1' a braking current for a motor 25 which may be traced from line 23 through circuit interruptor I5, stationary segment switch I4, stationary contact 26h of a multiple- I4a. of multiple-point point `circuit controller 26, conductors 21 and 23,

"a rectifier 23, motor windings and 3|, and by conductor 32 to the other supply line 24. Unidirectional current therefore ows through the rectier 29 and the motor windings 30 and 3l, which unidirectional current is effective to oppose rotation of the rotor of the motor 25 and when signal lamp 35a of the bank 35, which' circuit may be traced from stationary Contact 25h by cond uctcrs 21 and 28, resistor 3S. capacitor 31, sta-- tionary segment I3a of multiple-point switch I3.

spectlve contact segments.

control of the multiple-point switch I3. Y

YAfter connection of thermocouple I6 to the instrument I0 through the preamplifier 22, the

,printwheelf I I is moved transversely of the record chart 10c, a suitable index being simultaneously 'moved relative to the scale I 3b to indi-cate the magnitude of the temperature to which thermocouple I6 is subjected. After a predetermined time interval adequate to balance the measur- `4ing circuit, which may be of the potentiometer type disclosed in said Ross et al. patent, the printwheel II is moved downwardly into engagement with chart Illa to print thereon a numeral or 'other' character which is distinctive and serves to identify thermocouple I6. For example, the `print-wheel may have numerals 1-6. Thus, the aforesaid printing operation would place upon the chart Ia the numeral 1 indicating the measurement of the temperature to which the first thermocouple I6 of the series had been subjected.

After the printing operation, the printwheel I I is moved to its next position to bring the next numeral 2 into position preparatory to printing. Simultaneously, through the driving connection I2 the multiple-point switches I3 and I4 are advanced to complete. circuits through stationary contact segments 13b and I4b. During the initial movement of multiple-point switches i3 and I4 a cam Ia is rotated to open the circuit interruptor I5 prior to interruption of the i circuit through contact segment I4a. The circuit interrupter I5 thus performs the duty of opening and closing the circuit through each of the re- This is advantageous in avoiding any arcing at the multiple-point switch I4. Though the multiple-point switch I4 may comprise a plurality of circuit interrupters operable in sequence, it has been found more economical to provide the single circuit interrupter designed for the duty of making or breaking the motor control circuits. 1

' v Further in accordance with the invention, a

crest of cam I5a is moved against cam follower Ib to close circuit interrupter I5 after the multiple-point switches I3 and I4 have completed their respective circuits through contact segments I3b and I4b. When the circuit interruptor I5 is closed, an energizing circuit is completed through contact I4b, the stationary contact 251' of switch 25, conductors 40 and 4I, the motor windings 33 and 3l and by conductor 32 to the other supply line 24.

The motor 25 is thereupon energized to rotate the cams of switch 26 in a clockwise direction and in synchronism therewith to rotate the `cams of selector switch 42. Switch member 42g immediately moves under the control of cam 42a .the input circuit to preamplifier 22. The cam 42h, however, engages switch member 42h to connect thermocouple I1 to the input circuit prior to removal of thermocouple I6 therefrom. There is thus avoided any opening of the input circuit.

'Meanwhile the cam '25h moves its associated switch member to interrupt the motor energizing circuit through stationary contact 261' and to complete a braking circuit through the stationary -contact 251i whichl as before extends by Way of conductors 21 and 28, rectifier 29, through the motor windings and by conductor 32 to the other supply line 24. The motor 25 is thereupon braked to standstill with the braking circuit maintained through stationary contact 261i and the thermocouple I1 connected to the input circuit of preamplier 22. The measuring instrument Ill thereupon functions to move the print wheel II relative to the chart Ia preparatory to the printing of numeral 2 on the chart to record the temperature to which the thermocouple I1 is subjected.

It is again emphasized that the circuit interrupter I is operated by cam I5a to closed position after the circuit has been completed through ythe segment I4b, this operation being achieved by providing the cam I5a with narrower crests than the conducting segments of selector switch I4 so that the circuit through feach segment thereof is completed before closur of circuit interruptor I5, and so that each circuit thr'pugh each segment of the selector switch I4 is interrupted after the opening of the circuit interrupter I5.

With the foregoing understanding of the invention, it will be seen that after the measurement Vcapacitor 33, can flow from supply line 24 by way of lamp 35d, conducting segment I3d, capacitor 31, resistor 36, conductor '28, rectifier 29, through the `motor circuit and, hence, through contact 231i, segment I4d, and by way of circuit interrupter l5 to the other supply line 23. By reason of capacitor 31 in the foregoing circuit, only the ripple current of rectierrZB iiows through lamp 35d. The magnitude ,of the current flow provides a barely perceptible glow in the filament of lamp 35d and provides a distinctive signal that the motor-driven switches 26 and 42 are out of synchronism with the selector switches I3 and I4. vThe low intensity illumination of each signal lamp is desirable since it is then known that the lamp has not burned out and that asynchronous operation has occurred.

The foregoing signal persists as the motor 25 rotates switches 26 and 42 in clockwise'direction. Though cams 25D and 26e in turn move their switch members to engage stationary contacts 261i and 2q, braking circuits are not completed. The cams 42h and 42e in succession connect thermocouples I1 and I8 to measuring 1 instrument I0, but they are only momentarily of the temperature to which therrnocouple I1 is subjected, the system functions to measure in succession the temperatures to which thermocouples I8-2I are subjected.

In accordance with the present invention, it will be observed that the switch member of each single-pole, double-throw switch associated with each of cams 2Gb-26j is in contact with associated stationary contacts 261', 26m-26p for partial completion of an energizing circuit for rotation of motor '725. However, the switch member associated with cam 28a, is in engagement with stationary contact 26h.

By reason of the foregoing provisions, if motoroperated switches '26 and 42 should for any reason whatever getout of step or out of synchronism with selector switches I3 and I4, a motor-running circuit will be completed. For simplicity oi explanation, it will be assumed that a circuit will be completed through segment Idd of switch I4 but that motor-driven switches 25 and 42 are in the position shown in Fig. 1. Even though the switch member of cam 26a is engaging stationary contact 23h, the circuit therethrough will be broken at the segment I4a. However, there Will be completed an energizing circuit for the motor 25 which may be traced from supply line 23 through circuit interruptor I5, contact segment I4d, switch member associated with cam 26d, stationary contact 2571 conductors 40 and 4I, motor windings 30 and 3|, and by conductor 32 to the other supply line 24. Thus, the motor will be energized to rotate the switches 26 and 42 in clockwise direction.

It is to be observed the signal energizing circuit for the lamp 35a will be open at the conducting segment Ia. However, a current of small magnitude, small because limited by the impedance of the motor including phase-splitting vantages are great. Iessary to utilize relays.

connected to the input circuit since the motor 25 actuates the switches 23 and v42 at substantial speed with a small time interval between each circuit-controlling osition. ,Howeven as the cam '26d moves its :switch member into engagement with stationary contact 26r, a braking circuit is completed and `the motor 25 quickly comes to standstill with the switches 26 and 42 again in step or in synchronism with the selector switches I3 and I4. The signal lamp 35clis then energized with normal brilliance, since there is completed through contact 2E: an energizing circuit which extends by way of conductors 21 and 28 directly to the lamp 35d instead of through the motor, as previously described.

It will now be understood that similar synchronizing operations will automatically take place whenever motor-driven switches 26 and 42 get out of angular step with the selector switches I3 and I4 and that synchronization will be reestablished in a time interval which is small compared with the time interval of a few Seconds ordinarily required for the measuring instrument I0 to complete its cycle of measuring and recording operations for each thermocouple. Ac-

cordingly, even though asynchronous operation ture to which each thermocouple is subjected.

Though the control system is simple, its ad- It has not been found nec- Though relays could be utilized, as for example in place of the interrupter I5 and the cam I5a, greater reliability has been achieved without the use 'of such a relay and the possible service requirements incident to the use of relays. The system is rugged, foolproof and highly reliable. Neither the capacitor 31 nor the capacitor 33 is short--cir` cuited at any time by any of the contacts, thus avoiding possibility of welding or adherence of the contacts one to the other.

While a measuring instrument of the Vtype shown in said Ross et al. patent has been referred to as suitable for the instrument I0, it is to be understood that other types of measuring instruments can be utilized, such for example as shown in Williams Patent 2,113,164. A

In the foregoing description and in the claims,

cams 25d-2.6i. electrical equivalent of. the single-pole, doubleaes-asie reference hss` been made to the Singh-D018.. doll- .ble-.throw switch associatedv with each of the Itis to be understood that any 'throw switch is; intended to be covered by the term though there be more than a single movable switching element.

Furtherv in connection with the braking circuit, it. is to be observed that the now of unidirectional current from the rectifier 29 is through winding 30 and then in series through winding 3| of the motor 25. Thus, the ripple current is in phase in the respective motor windings 3ll and 3| in avoidance of development of torque by the motor 2,5. which would tend to I to be understood that a single cam may be utilized with each multiple-point switch disposed at a 60 angle with respect to the crest of the single cam. Thus, each switch would be operated in manner described for the controller 25 by the Acrest of the single cam. In one embodiment of the invention this arrangement has proved to be entirely satisfactory. `Similarly, a single cam could be utilized for the multiple-point circuit controller 42.

switch or circuit controller can be provided with any desired number of points or switch positions,

Obviously, each multiple-point the only limit being the physical size of the assembly, the angular disposition of each switch where located in annular -array about a single cam being Varied according to the number of switches or points to be utilized.

Referring to Fig. 2, there has been illustrated diagrammatically a fractional part of the system of Fig. l. with` circuit variations to simplify the signalling circuits. As in Fig. 1, through mechanical connection l2 which, of course, may be a shaft, a cam 50 is rotated in synchronism with the printwheelv of the recorder l!! of Fig. 1 to operate the multiple-point switch 49. Instead of the conducting segments of the multiplepoint switch I4, there have been shown in Fig. 2 individual circuit interrupters 5|, 52 and 53 which .in conjunction with cam 50 perform the dual functions of the multiple-point switch I4 and the circuit interrupter I5 of Fig. 1. The cam 50 and the arrangement of the, circuit interrupters 5|- 53 are also illustrative of the single cam arrangement above described with reference to multiplepoint controllers 26 and 42.

For convenience, the multiple-point controller 26 has been illustrated with three circuit-controlling points, at each of which there is provided a single-pole, `double-throw switch, the operation f each of which is under the control of the cams 26a, 2Gb and 26e. The braking circuit is. shown established from supply line 23 by way of circuit interrupter in closed position by the crest of cam 50, the stationary contact 26h, a rectifier or diode 55 of the gaseous conduction type such as mercury vapor, and by way of windings 3G and 3| of motor 25 to the other supply line 24. Advantage is taken of the fact lthat such a rectifier, particularly of the mercury vapor type, has a. pronounced color, as bluishgreen, when operating near full capacity. Thus,

the. rectier will have a distinctive color as compared with the, color Qi reoters 5.6- and 5lconnected, in. branches of. the braking circuit which have not yet. been connected t0 the alternating source.- Inasmuch as each or rectiflers 55.-51 has a hot cathode, the filament supplycircuits being omitted for sake of simplicity, therewill be visible in each rectier tube the reddish glow of the heated cathode which will provide an indication that each tube'is operative and ready for operation when a brakingA circuit is completed therethrough` f v When the cam 5.0 is advanced to the angular position corresponding with the location of the circuit interrupter 5 2, the foregoing braking circuit throughA rectifier 55 will have been broken and the circuit through interrupter 52A will be completed to establish an energizing circuit through stationaryL contact 251' and by conductor 54;, motor windings. 3Q and 3| to the other supply line 2li.A Thus, the motor 25 will be energized to rotate the cams 26a-26e in a clockwise direc,- tion until cam 2Gb operates its associated single- .pole, double-throw switchY to interrupt the motor- Aenergizing circuit through contact 261 and to complete a braking circuit through stationary Contact 26j' for flow of unidirectional braking current through rectifier 5E, and thence through the motor windings. in manner previously described. Thus, the r'ccter 5.5 will again indicate that the multiple-point circuit controller 26 has an angular position corresponding with that of the multipie-point switch 48.

In order that there be adequate braking current, it is desirable, if not necessary, that each of the rectiflers 55-51 have a low potential drop. That is to say, that they be selected or designed for fiow therethrough of adequate current quickly to brake the motor 25 to standstill.

In the event of asynchronous operation, the system operates in the same manner as the system of Fig. l to bring the multiple-point switch 26 into synchronism or predetermined angular relation with the multiple-point switch 49..

Other changes within the scope of the appended claims may now suggest themselves to those skilled in the art.

What is claimed is:

1. A control system comprising a first multiplepoint circuit controller, means for advancing said circuit controller from one circuit-controlling Aposition to another, a second multiple-point circuit controller including at each point a singlepole, double-throw switch, each of said switches, except one, being in corresponding circuit-controlling positions. a, drivimg motor for operating said switches in sequence between circuit-controlling positions, an energizing circuit for said driving motor partially completed through said switches in their corresponding switch positions and which energizing circuit is completed by movement of said rst multiple-point controller from one position to another, the resultant energization and rotation of said motor thereafter opening its said energizing circuit through one of said single-pole, double-throw switches, and a braking circuit completed by said last-named single-pole, double-throw switch for bringing said motor and said second multiple-point controller to standstill in predetermined angular relation with said first multiple-point controller.

2. The combination set forth in claim 1 in which there is provided a third multiple-point .forsaid nrst multiple-point controller also actuating said third controller in synchronism therewith, an energizing circuit for said signal- ,ling means completed by said ,third controller,

said energizing circuit being connected to said ,motor circuit for application of a lower degree ,of energization when said second multiple-point circuit controller is out of predetermined angu- ,lar relation with said rst multiple-point circuit controller, means for advancing said circuit controller from one circuit-controlling position to another, a second multiple-point circuit conv:'troller including at each point a single-pole,

ldouble-throw switch, each of said switches, except one, being in corresponding circuit-controllingpositions, a driving motor for operating said switches in sequence between circuit-controlling 'positions and for operating the transfer switch uin synchronism therewith, an energizing circuit ,l for said drivingmotor partially completed with said switches in said corresponding switch positions and which energizing circuit is completed `by movement of said rst multiple-point oontroller from one position to another, the resultant energization and rotation of said motori/opening said energizing circuit through the 'singlepole, double-throw switch connected to the point of said first multiple-point controller to which it has been operated, and a braking circuit completed by said last-named single-pole, doublethrow switch for bringing said motor and said second multiple-point circuit controller to standstill in predetermined angular relation with said rst multiple-point controller.

4. A signalling system for a controller including a multiple-point circuit controller having a plurality of single-pole, double-throw switches operable in sequence between their circuit-controlling positions, a motor for advancing said circuit controller for operation of first one of said switches and then another, an alternating current energizing circuit for said motor normally partially completed by all except one of said single-pole, double-throw switches while in corresponding circuit-controlling positions, a braking circuit for said motor partially completed by said one of said single-pole, double-throw switches, said braking circuit including a rectifier, a first multiple-point switch having each point thereof connected in series with one of said single-pole, double-throw switches for completion of said braking circuit when in angular rclation corresponding with said one of said switches, a second multiple-point switch operable with said first multiple-point switch, signalling means corresponding with each position of said second multiple-point switch and including an energizing circuit controlled thereby, said energizing circuit for said signalling means including a part, and being under the control, of said braking circuit for normal energization of said signalling means.

5. A signalling system for a controller including a multiple-point circuit controller having a plurality of single-pole, double-throw switches operable in sequence between their circuit-controlling positions, a motor for advancing said circuit controller for operation of nrst one of said switches and then another, an alternating ,current energizing circuit for said motor norinally partially completed by all except one of said single-pole, double-throw switches while in corresponding circuit-controlling positions, a

Abraking circuit for said motor partially completed by said one of said single-pole, double-throw switches, said braking circuit including a rectiiier, a multiple-point switch having each point thereof connected in series with'l'oneof said single-pole, double-throw switches for completion of said braking circuit when in angular relation corresponding with said one ofsaid switches, a second multiple-point switch operable with said rst multiple-point switch, signalling means corresponding with each position of said second multiple-point switch and including an energizing circuit controlled'thereby, said energizing Vcircuit for said signalling means including a part, .and being under the control, of said braking circuit for normal energization of said signalling means, and upon asynchronous operation of ,said

Acontroller 'and said multiple-point switch said signalling circuit having reduced energization t Isignal said asynchronous operation. v

.6. A signalling system for a controller including a multiple-point circuit controller having a Vplurality of single-pole, double-throw switches Voperable in sequence between their circuit-controlling positions, a motor for advancing said circuit controller for operation of rst one of said switches and then another, an alternating cur- `rent energizing circuit for sa'id motor normally partially completed by all except one of said single-pole, double-throw switches while in corresponding circuit-controlling positions, a braking circuit for said motor partially completed by said one of said single-pole, double-throw switches, said braking circuit including a rectifier, a multiple-point switch having each point thereof connected in series with one of said single-pole, double-throw switches for completion of said braking circuit when in angular relation corresponding with said one of said switches, a second multiple-point switch operable with said first multiple-point switch, signalling means corresponding with each position of said second multiple-point switch and including an energizing circuit controlled thereby, said energizing circuit for said signalling means including a part, and being under the control, of said braking circuit for normal energization of said signalling means, and upon asynchronous operation of said controller and said multiple-point switches said signalling circuit extending through said rectifier and through said motor for application of substantially ripple current only to said signalling means to indicate said asynchronous operation.

7. A control system for the multiple-point transfer switch of a multiple-point measuring instrument, comprising a iirst multiple-point circuit controller, means for advancing said circuit controller from one circuit-controlling position to another, a second multiple-point circuit controller including at each point a single-pole, doublethrow switch, each of said switches, except-one, being in corresponding circuit-controlling positions, a driving motor having motor windings for operating said switches in sequence between circuit-controlling positions, an alternating current energizing circuit for said driving motor partially completed with said switches in said corresponding switch positions and which energizing circuit is completed by movement of said first multiple-point controller from one position to another, the resultant energiaation and rotation A:first multiple-point.controller; Seid. Prekrlclrcuit including Ainiseries thereinaidwindingsfgr .flow in phase .therethroughof the ripple current from said rectifierin avoidance otdeyelopmerit lottorqie by Said motor due to said.- ripple current. 1.5

8: Al'i control system comprising a rst multiplepint switch; means fr advancing the switch `fioin one circuit-controlling position to another, f driving i'nbto'r, a s'econdfmuitiple-povint Switch 'si-bi byY said drivin-g motor fi-omeneeireuiii ejeidy 'S'id sord switct, and a iii-airing circuit tl'rv said motor completed upon arrival of said edifici switch.. in its said predetermined angular positii duickly to bring' said second Switch iidsad riiotdi` to standstill, said braking circlt riiili'i'li'iingV b'ainches'ne for each point of said seond multiple-peint switch and inciudifi in each branch` a'. rectifier of the gaseous ,discharge type which by it'sv distinctive color' indicates the arrival of said second multiple-point switchl in predetermined angular relation with said rs't multiple-point switch. n y y W111i MCADAM.

ketenen-ces cited iii the 'iiie f i-.iiis paient. UNITED S'ATES AENTs Number Namev Date 1,965,393 Schleicher July 3; 1934 2;428,402 Wint'erbttomV Oct. 7, 1947 2,430,113 Handley v Nov.l 4, 1947 v 2;430,125 Kiimis` Nov. 4, l947 2,478,221 Alford Allg; 9, 1949 2,502,215 Giffen et al z Mar. 28, 1950 2,549,401 i Stein et al. Apr; 17, 1951 FO'RIG PATENTS Number Country 4 'Date y I 562,264 Germany ;.i.- Oct. '24, 1932 

